add (optional) diff and text columns to output.

tables.py

@@ -218,3 +218,11 @@ class RevisionCollapsed(RevisionField[int]):
 
     def extract(self, page: mwtypes.Page, revisions: list[mwxml.Revision]) -> int:
         return len(revisions)
+
+
+class RevisionText(RevisionField[str]):
+    field = pa.field("text", pa.string(), nullable=False)
+
+    def extract(self, page: mwtypes.Page, revisions: list[mwxml.Revision]) -> str:
+        revision = revisions[-1]
+        return revision.text